The present invention relates to a tractor-trailer data transmission path or link forming part of a mobile communication system to allow data transmission back and forth between a tractor and attached trailer for subsequent transmission to a remote monitoring center.
Mobile communication systems are used by commercial trucking companies to locate, identify and ascertain status of their vehicles, as well as to allow the vehicle operator to send and receive information. One major problem facing large trucking companies is keeping track of the location of all trailers throughout the country. When trailers are unhooked from a tractor, they are liable to be left at a location and potentially forgotten. This results in unnecessary down time and substantial economic impact on the company.
In addition to keeping track of the location of all trailers at all times, it is also desirable to be able to ascertain the condition of trailer equipment, environmental conditions in a trailer, as well as the condition of the payload. This may be achieved by placing various sensors in the trailer. The sensors are typically connected to a suitable memory unit in the trailer in which trailer identification and cargo information is stored, and the sensor outputs as well as the trailer identification must be transmitted to the tractor over a suitable transmission medium. Trailer information is therefore transmitted to the tractor for transmission to a central facility where the information is monitored. Up to now, various transmission mediums have been contemplated including RF transceivers, infrared transceivers, dedicated wiring, and a sharing of existing wiring. RF and infrared transmission schemes can be costly and susceptible to interference. Dedicated wiring are not desired since additional connectors or a complete rewiring of existing trailers would be required. The preferred technique has been directed towards transmitting the information from trailer to tractor via existing tractor-trailer electrical wiring which provides power for the trailer lights as well as for equipment in the trailer. However, when the information signal is modulated onto a carrier and impressed upon the electrical power line, it is sometimes not easy to pick out the signal.
One tractor-trailer communication system of this type is described in application Ser. No. 07/620,133, filed Nov. 30, 1990, of Moallemi et al., which is a Continuation of application Ser. No. 07/339,686, filed Apr. 18, 1989, now U.S. Pat. No. 5,142,278 issued Aug. 25, 1992, the disclosure of which is incorporated by reference.